Only skip using the DT cookie when connecting to an OIE domain

[epierce]

Description

The recent changes to skip sending the DT cookie in force_classic mode also affected Okta Classic domains. This change ensures that DT cookie only gets skipped when connecting to an OIE domain.

Types of changes

• [x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x ] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• [x ] I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• [x ] All new and existing tests passed.